1. Field
One or more embodiments described herein relate to a display device.
2. Description of the Related Art
A liquid crystal display is one of the most widely used flat panel displays. A liquid crystal display may include two display panels equipped with electric field generating electrodes (such as a pixel electrode and a common electrode), a liquid crystal layer interposed between the two panels, a data driver for supplying data voltage, a gate driver for supplying a gate signal, and a signal controller for controlling the data driver and the gate driver. A liquid crystal display may also include a plurality of signal lines, such as gate lines and data lines for applying data voltages to pixel electrodes by controlling switching elements connected to the pixel electrodes.
Each pixel electrode may be connected to a switching element (such as a thin film transistor (TFT)) and receives the data voltage. An opposing electrode may be formed throughout an entire surface of the display panel and may receive a common voltage (Vcom). A desired image may be displayed by applying the data voltage and the common voltage to the pixel electrode and the opposed electrode, respectively. Applying these voltages generates an electric field in the liquid crystal layer. An intensity of the electric field may be controlled in order to control transmittance of light passing through the liquid crystal layer.
In one arrangement, the liquid crystal display may receive an input image signal from an external graphic controller. The input image signal stores luminance information of each pixel, and each pixel may be applied with a data voltage corresponding to desired luminance information. The data voltage applied to the pixel is represented as pixel voltage, according to a difference from the common voltage applied to the common electrode. Each pixel displays a luminance represented by a gray scale value of the image signal according to the pixel voltage.
In this case, the polarity of the data voltage for voltage which becomes a reference voltage for each frame, each row, each column, or each pixel may be inverted in order to prevent a degradation which occurs upon long-time application of a unidirectional electric field to the liquid crystal layer. Further, the polarities of pixel voltages represented by adjacent pixels may be different from each other, in order to prevent streaks such as vertical lines in a display screen from being generated.
In particular, the polarity of one pixel voltage may rise from a negative polarity to a positive polarity, and the polarity of another pixel voltage may fall from a positive polarity to a negative polarity. These polarities may be different from each other in response characteristics due to characteristics of the liquid crystal. For example, a rising speed of the pixel voltage may be lower than a falling speed of the pixel voltage when a general liquid crystal is driven. This difference in response speed may cause changes in luminance.
The change depending on response speed may not be substantially problematic when the liquid crystal display is driven at a high frequency, but the luminance difference may be visually recognized when the liquid crystal display is driven at a low frequency. Referring to a temporal contrast sensitivity function (TCSF), even though an actual luminance change is small particularly when the liquid crystal display is driven at a low frequency of 10 Hz or less, it is recognized as if the luminance change is large. As a result, a flicker may be viewed to thereby degrade display quality.